Communication networks such as computer data networks may be partitioned in many different manners. In many cases, a company or enterprise may have a local area network that may be separated from the Internet or other wide area networks through a gateway or firewall. In many cases, a private or internal network may use certain communications protocols that may be different than those used outside the network.
Further, various security mechanisms may be available to authenticate two devices and encrypt communications between the two devices. The security mechanisms may be used for cases where sensitive information is being passed and where authentication may be desired between the two devices.
A TCP/IP model has been used to describe many aspects of network architectures. Layer 5, the application layer, may be used by most programs for network communication. Data may be passed from the program in an application-specific format, then encapsulated into a transport layer protocol. Layer 4, the transport layer, includes end to end message transfer capabilities independent of the underlying network. Layer 3, the network layer, may perform the tasks of getting packets of data from source to destination. Layer 2, the data link layer, may describe various methods used to move packets between hosts. Layer 1, the physical layer, may describe the encoding and transmission of data over network communications media.